Press the switch to lower the walls. Kill the two, four or seven mancubi and more walls will lower, revealing arachnotrons. Kill them all and you will be able to end the level by pressing the eye switch in the middle of the map. Use the blur spheres to avoid the monsters.
Before you exit, hit the switches in this room and the platforms the mancubi were on will lower, revealing health and weapons. Also, get the ammo and health from where the arachnotrons came. Now go back to the center of the map and exit.

The only secret in this level is the area surrounding the exit switch. (sector 1) Therefore, it is impossible to exit the level without triggering the secret, unless you use the alternative exit switch described below or rocket jump to it without raising the step, as happens in UV speed demo on this level by Marijo "Sedlo" Sedlic (see below).

The northwest corner of the map has a secret alcove, housing a BFG9000 and an energy cell pack, along with another exit switch. In single player or coop, it is inaccessible; it is only opened when a deathmatch player spawns in that location. This is usually discovered when a player uses the iddt or idclipcheat codes. If a player enters the region through noclip cheat, it can be disabled safely because the wall can be opened from inside.

A possible bug or warning that occurs is that if the last two arachnotrons die at the same time, it may cause the stair step surrounding the exit in the center to rise twice, making the exit in the center become seemingly inaccessible, but if this happens, you can still access the exit by running across from the lowered northwest or northeast platforms.

Not really a bug, but more of a warning. If this level is played on Nightmare! difficulty or with the -respawnparameter set, the arachnotrons that endlessly respawn may cause the stair step that surrounds the center exit to continuously rise each time all of them die, making the exit in the center inaccessible.

Because the normal route through the map involves killing all of the monsters on the level, it was for long believed that a UV pacifist run of this map was impossible. However, Drew DeVore (stx-Vile) proved this wrong in 2005 by releasing a demo demonstrating that it is possible to complete the level if the player propels himself to the exit switch with a rocket launcher.

Normally, the level is finished with 100% secrets, so a separate category from NM speed would be redundant. All secrets are found unless the noclip bug occurs or the map is completed by using a rocket jump without touching the exit sector's floor.

The alcove in the northwest corner contains a BFG9000, a bulk cell and an additional exit switch (as the central exit is usually not reachable when using -nomonsters on deathmatch mode). However, this alcove is accessible only in deathmatch mode, after a player spawns inside and opens the door.

The backpack at the start of the level is actually ten backpacks placed on top of each other. Picking "it" up will thus give the player a very large amount of ammo.

"Dead Simple" is the first official map in the Doom series whose name is not a noun or a noun phrase.